package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        // 设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData( value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback
            , Long time, TimeUnit unit){
        String key =keyPrefix + id;
//        1.从redis中查找缓存
        String shopid = stringRedisTemplate.opsForValue().get(key);

        // 2.判断是否存在
        if (StrUtil.isNotBlank(shopid)){
            //3.存在则返回
            return JSONUtil.toBean(shopid,type);
        }

        //判断命中的是否是空值
        if (shopid!= null){
            return null;
        }
        //4. 不存在则根据id 查询数据库
        R r = dbFallback.apply( id);
        //5.不存在,则返回错误
        if (r == null)
        {
            // 不存在的情况下,写入空值
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.查询后,放入redis缓存中
        this.set(key,r,time,unit);
        // 7.返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,
             Long time, TimeUnit unit){
        String key =keyPrefix + id;
//        1.从redis中查找缓存
        String shopid = stringRedisTemplate.opsForValue().get(key);

        // 2.判断是否存在
        if (StrUtil.isBlank(shopid)){
            //3.不存在则返回
            return null;
        }

        // 4.命中,需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopid, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if(expireTime == null || expireTime.isAfter(LocalDateTime.now())) {
            //5.1 未过期,直接返回店铺信息
            return r;
        }
        //5.2 过期,缓存重建
        //6.缓存重建
        //6.1 获取互斥锁
        String lockkey =LOCK_SHOP_KEY + id;
        boolean islock = tryLock(lockkey);
        //6.2 判断是否获取成功
        if (islock) {
            //6.3 成功,开启独立线程,实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                   //查询数据库
                    R r1 = dbFallback.apply(id);
                    // 写入redis
                this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    // 释放锁
                    unLock(lockkey);
                }
            });
        }
        //6.4 缓存过期的店铺信息
        return r;
    }

    public boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    public void unLock(String key){
        stringRedisTemplate.delete(key);
    }
}
